Make SSE inclusion conditional for target features (#526)

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## [Unreleased]
 
+* Bump `librocksdb-sys` up to 6.19.3 (olegnn)
+* Make SSE inclusion conditional for target features.
+  RocksDB is not compiled with SSE4 instructions anymore unless the corresponding features are enabled in rustc (mbargull)
 * Bump `librocksdb-sys` up to 6.20.3 (olegnn, akrylysov)
 * Add `DB::key_may_exist_cf_opt` method (stanislav-tkach)
 * Add `Options::set_zstd_max_train_bytes` method (stanislav-tkach)

librocksdb-sys/build.rs

@@ -103,16 +103,26 @@ fn build_rocksdb() {
         // This is needed to enable hardware CRC32C. Technically, SSE 4.2 is
         // only available since Intel Nehalem (about 2010) and AMD Bulldozer
         // (about 2011).
-        config.define("HAVE_SSE42", Some("1"));
+        let target_feature = env::var("CARGO_CFG_TARGET_FEATURE").unwrap();
+        let target_features: Vec<_> = target_feature.split(",").collect();
+        if target_features.contains(&"sse2") {
             config.flag_if_supported("-msse2");
+        }
+        if target_features.contains(&"sse4.1") {
             config.flag_if_supported("-msse4.1");
+        }
+        if target_features.contains(&"sse4.2") {
             config.flag_if_supported("-msse4.2");
+            config.define("HAVE_SSE42", Some("1"));
+        }
 
         if !target.contains("android") {
+            if target_features.contains(&"pclmulqdq") {
                 config.define("HAVE_PCLMUL", Some("1"));
                 config.flag_if_supported("-mpclmul");
             }
         }
+    }
 
     if target.contains("aarch64") {
         lib_sources.push("util/crc32c_arm64.cc")